FCC Technician Class Exam Study Guide - 2014-2018/Subelement T3 Group C

Propagation modes: line of sight; sporadic E; meteor and auroral scatter and reflections; tropospheric ducting; F layer skip; radio horizon

Question 1

 * Why are direct (not via a repeater) UHF signals rarely heard from stations outside your local coverage area?
 * A. They are too weak to go very far
 * B. FCC regulations prohibit them from going more than 50 miles
 * C. UHF signals are usually not reflected by the ionosphere
 * D. They collide with trees and shrubbery and fade out

The correct answer is C.

Question 2

 * Which of the following might be happening when VHF signals are being received from long distances?
 * A. Signals are being reflected from outer space
 * B. Signals are arriving by sub-surface ducting
 * C. Signals are being reflected by lightning storms in your area
 * D. Signals are being refracted from a sporadic E layer

The correct answer is D.

Question 3

 * What is a characteristic of VHF signals received via auroral reflection?
 * A. Signals from distances of 10,000 or more miles are common
 * B. The signals exhibit rapid fluctuations of strength and often sound distorted
 * C. These types of signals occur only during winter nighttime hours
 * D. These types of signals are generally strongest when your antenna is aimed west

The correct answer is B.

Question 4

 * Which of the following propagation types is most commonly associated with occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?
 * A. Backscatter
 * B. Sporadic E
 * C. D layer absorption
 * D. Gray-line propagation

The correct answer is B.

Question 5

 * Which of the following effects might cause radio signals to be heard despite obstructions between the transmitting and receiving stations?
 * A. Knife-edge diffraction
 * B. Faraday rotation
 * C. Quantum tunneling
 * D. Doppler shift

The correct answer is A.

Question 6

 * What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?
 * A. Tropospheric scatter
 * B. D layer refraction
 * C. F2 layer refraction
 * D. Faraday rotation

The correct answer is A.

Question 7

 * What band is best suited for communicating via meteor scatter?
 * A. 10 meters
 * B. 6 meters
 * C. 2 meters
 * D. 70 cm

The correct answer is B.

Question 8

 * What causes tropospheric ducting?
 * A. Discharges of lightning during electrical storms
 * B. Sunspots and solar flares
 * C. Updrafts from hurricanes and tornadoes
 * D. Temperature inversions in the atmosphere

The correct answer is D.

Question 9

 * What is generally the best time for long-distance 10 meter band propagation via the F layer?
 * A. From dawn to shortly after sunset during periods of high sunspot activity
 * B. From shortly after sunset to dawn during periods of high sunspot activity
 * C. From dawn to shortly after sunset during periods of low sunspot activity
 * D. From shortly after sunset to dawn during periods of low sunspot activity

The correct answer is A.

Question 10

 * What is the radio horizon?
 * A. The distance over which two stations can communicate by direct path
 * B. The distance from the ground to a horizontally mounted antenna
 * C. The farthest point you can see when standing at the base of your antenna tower
 * D. The shortest distance between two points on the Earth's surface

The correct answer is A.

Question 11

 * Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations?
 * A. Radio signals move somewhat faster than the speed of light
 * B. Radio waves are not blocked by dust particles
 * C. The Earth seems less curved to radio waves than to light
 * D. Radio waves are blocked by dust particles

The correct answer is C.

Question 12

 * Which of the following bands may provide long distance communications during the peak of the sunspot cycle?
 * A. Six or ten meters
 * B. 23 centimeters
 * C. 70 centimeters or 1.25 meters
 * D. All of these choices are correct

The correct answer is A.